This invention relates to a simplified, highly efficient driving system for producing, from a-c power line voltage, adjustable amplitude and frequency alternating voltage to drive an a-c induction motor, while at the same time minimizing power losses and energy consumption.
Inverter systems have been employed to convert fixed frequency a-c power line voltage to variable frequency and amplitude alternating voltage for operating an a-c induction motor, but most of these systems are very inefficient in that highly distorted current waveforms, having substantial harmonic content, result, causing excessive power losses in both the inverter and the motor, excessive motor heating and noisy (hum) motor operation. These shortcomings are particularly pronounced when the motor is of the single phase type.
The motor driving system of the present invention is a significant improvement over the prior systems since a much higher efficiency level is attained, making the invention particularly attractive when used to drive a single phase a-c induction motor. Moreover, the driving system of the invention has different operating modes in which enhanced power savings and energy reduction are achieved.